生物降解材料聚乙醇酸的溶液化学

The interests in aliphatic polyesters for biomedical engineering use have increased dramatically. Polyglycolic acid is the simplest aliphatic polyester and widely used in biomedical fields because it has good biodegradability, biocompatibility, and mechanical properties. In addition, polyglycolic acid can also be used for packaging material and agricultural biological degradable film etc. However, hexafluoroisopropanol is the only reported solvent for polyglycolic acid at room temperature. This has hindered its application in other fields. In recent years, the studies on in vitro and in vivo degradation as well as modification of polyglycolic acid are very active. Either using for packaging material or agricultural film, polyglycolic acid needs to be processed at melting state. However, research on degradation under melting state has not been reported. This project focuses on studying the following questions. Solubility parameters of polyglycolic acid and its solvents will be investigated to reveal the interaction between polyglycolic acid molecules and solvent molecules and then to find the good solvents of polyglycolic acid; The thermodynamics parameters-theta temperature will be determined to revealed the microscopic properties of polyglycolic acid solutions and to analyze the reason why polyglycolic acid does not dissolve in other solvents from thermodynamic and solution chemistry points of view; Under melt hydrolysis, the surface morphology, crystallinity, molecular weight and melt point of polyglycolic acid will be studied to explore degradation mechanism; The results to be obtained in this item will provide theoretical support for further application and relative research of polyglycolic acid.

可降解脂肪族聚酯因应用广泛引起人们极大地关注。聚乙醇酸是最简单的聚酯，具有良好的生物降解能力、生物相容性和机械性质，除广泛应用于生物医学领域外，还用于包装材料及农用生物降解薄膜等领域。室温下聚乙醇酸除六氟异丙醇外不溶于其他溶剂，已阻碍其在其他领域的应用。相关的研究集中在改性和体外与体内降解。然而，不管是用于包装材料或农用薄膜，都是在熔融条件下加工而成的，而熔融条件下的降解研究却未见报道。本项目拟通过研究聚乙醇酸及溶剂的溶度参数来揭示聚乙醇酸分子与溶剂分子的相互作用，进而找到聚乙醇酸的良溶剂；通过对热力学参数-θ温度的测定，揭示聚乙醇酸溶液的微观性质，从热力学和溶液化学的角度分析聚乙醇酸难溶的原因；深入研究熔融条件下聚乙醇酸水解降解过程中的表面形貌、结晶度、分子量、熔点随时间的变化关系，探索聚乙醇酸熔融降解机理；本项目拟获得的研究结果将为聚乙醇酸的应用及相关研究提供理论支持。

聚乙醇酸具有良好的生物降解性和相容性，广泛应用于医学、包装材料及农用生物降解薄膜等领域。在使用过程中，涉及到聚乙醇酸与其他分子之间相容性或相互作用。而溶度参数、相互作用参数等能定量描述聚合物分子与其他分子之间的相互作用。但这方面的研究却鲜有报道。所以，对聚乙醇酸溶液性质的研究需进一步深入。如：聚乙醇酸与其他溶剂形成的溶液在什么热力学条件下表现出理想溶液的行为？另外，近年来对聚乙醇酸降解的研究仅局限于模拟体内环境的体外降解的研究，而其他条件下的降解如熔融状态下水解的研究却未见报道。. 为提供严谨的聚乙醇酸溶度参数数据，本项目采用正交设计法优化计算溶度参数；为研究聚乙醇酸溶液理想状态下的性能及分子微观结构，采用相平衡等方法确定溶液的θ温度；为研究熔融条件下聚乙醇酸水解机理，建立了聚乙醇酸熔融状态下的降解动力学方程。. 实验室合成的聚乙醇酸和外购聚乙醇酸的三维溶度参数分别为：δd=17.094 (MPa)1/2、δp＝8.206 (MPa)1/2、δh＝7.912 (MPa)1/2 ；δd=17.35 (MPa)1/2、δp＝8.66 (MPa)1/2、δh＝9.87 (MPa)1/2。合成聚乙醇酸–溶剂体系的体积修正系数α = 1.54~1.62，外购聚乙醇酸–溶剂体系的体积修正系数α = 0.88~0.91。同时，获得了两种聚乙醇酸与43种溶剂、36种溶剂的相互作用参数。使用了几十种溶剂，保证了数据准确可信，丰富了聚乙醇酸的理化数据库，为聚乙醇酸的进一步使用提高了理论依据。. 研究了熔融状态下聚乙醇酸的降解规律，考察了介质pH值、质量、结晶度、分子结构等随时间的变化关系，建立了相应的动力学方程。获得的结果为聚乙醇酸的进一步应用奠定了理论基础。. 测定了聚乙醇酸在N-甲基吡咯烷酮、苯甲醇、苯胺和间甲酚中的θ温度。聚乙醇酸—N-甲基吡咯烷酮溶液、聚乙醇酸—苯甲醇溶液、聚乙醇酸—苯胺溶液和聚乙醇酸—间甲酚溶液的θ温度分别 为429.92K、430.85K、437.45K、449.03K。获得的θ温度数据填补了聚乙醇酸溶液热力学性质的空白，为研究其溶液理想状态下的性能提供了坚实的理论基础。